biomechanics of running indicates endothermy in bipedal dinosaurs生物力学的运行表明在两足恐龙是温血动物.pdf

Biomechanics of Running Indicates Endothermy in Bipedal Dinosaurs 1 2 2 Herman Pontzer *, Vivian Allen , John R. Hutchinson 1 Department of Anthropology, Washington University, St. Louis, Missouri, United States of America, 2 Structure and Motion Laboratory, Department of Veterinary Basic Sciences, The Royal Veterinary College, London, United Kingdom Abstract Background: One of the great unresolved controversies in paleobiology is whether extinct dinosaurs were endothermic, ectothermic, or some combination thereof, and when endothermy first evolved in the lineage leading to birds. Although it is well established that high, sustained growth rates and, presumably, high activity levels are ancestral for dinosaurs and pterosaurs (clade Ornithodira), other independent lines of evidence for high metabolic rates, locomotor costs, or endothermy are needed. For example, some studies have suggested that, because large dinosaurs may have been homeothermic due to their size alone and could have had heat loss problems, ectothermy would be a more plausible metabolic strategy for such animals. Methodology/Principal Findings: Here we describe two new biomechanical approaches for reconstructing the metabolic rate of 14 extinct bipedal dinosauriforms during walking and running. These methods, well validated for extant animals, indicate that during walking and slow running the metabolic rate of at least the larger extinct dinosaurs exceeded the maximum aerobic capabilities of modern ectotherms, falling instead within the range of modern birds and mammals. Estimated metabolic rates for smaller dinosaurs are more ambiguous, but generally approach or exceed the ectotherm